Prior to casting a molten metal, such as molten steel, refining wires can be injected into the molten metal vessels such as a ladle, pot or continuous casting tundish, to provide the metal with improved characteristics. The purpose of the refining wire is to inject refining materials, such as metals and/or minerals, encapsulated in the sheath of the wire into the molten metal in accurate quantities and in a controller manner, when the refining materials display either a high affinity to oxygen, or a low melting and/or vapor point, or a high vapor pressure, or a low solubility or law density compared to the molten metal, or a combination of these factors. In this regard, it is important to achieve a high percentage of recovery of the refining material defined as the ratio of the injected material quantity remaining into the molten metal divided by the total material quantity injected.
In a known method manufacturing a refining wire, a steel strip is rolled to form a U-shaped section that is filled with refining material in powered form. The two longitudinal edges of the U-shaped strip section, which have been pre-folded to that effect, are then hooked together. In this manner, a refining wire is formed with the steel sheath encapsulating a core of refining material.
Another method of manufacturing a refining wire is the same as above with the exception that the refining material is introduced into the U-shaped section as a solid extruded wire.
Refining wires produced by these known methods usually have a sheath thickness in the range of 0.2 mm to 0.6 mm due to the manufacturing and product constraints. As a result, the wire can be deformed easily by the high pressure of the feeder pinch rolls used to inject the wire through a guide tube into the molten metal vessel, thereby requiring guide tubes with comparatively large inner diameters which are detrimental to guiding the refining wire accurately into the vessel.
Sometimes also, the refining wire is not sufficiently rigid to penetrate a solidified surface of slag floating on the surface of the molten metal, such as molten steel, in the vessel.
Further, the hook-type closure for the steel sheath of the wires discussed above does not allow for the deep rolling or drawing of such wires down to much smaller diameters, in which case, the core can include excessive and undesirable amounts of air which, during the refining process, is detrimental to the quality fo the molten metal as well as the recovery of the core material. Moreover, the refining material can interact with the components of the air or other materials, such as moisture or oxidizing agents, thus reducing the shelf life of the wire.
It is an object of the present invention to provide a refining wire that overcomes, or at least substantially reduces, the disadvantages associated with the known refining wires discussed above.
It is another object of the invention to provide a refining wire and associate method of manufacture, with a sheath thickness which is larger than those of the known refining wires discussed above, resulting in improved manufacturing techniques for refining molten metals, particularly molten steel.